1. Field of the Invention
This invention relates to folders and more particularly to systems and methods for folding continuous web into one or more stacks in large volume and at high speed.
2. Background Information
In high-speed, large-volume printing operations, such as those employed in bulk-mailing activities and print-on-demand applications, it is quite common to use a continuous web that contains printing and other enhancements. This web is transferred through a variety of operations within the overall printing system. A printed web may be fed initially to downstream web utilization devices (such as printers, embossers, cutters and folders) using a driven roll stand that pays out web from a source roll as the web is drawn by the downstream devices. The web may, at various time in the process be draw up onto a take-up roll for refeeding to a further downstream web-utilization process. At some stage in the process it may be desirable to maintain the web in continuous form, but render it into one or more stacks of folded continuous web. Typically, web is folded into a stack in a “zigzag” fashion in which individual, substantially equal-length sections or pages are folded atop one another. Often, the web includes widthwise perforations, crease lines or other stress-relief points that facilitate folding by a set of folder beater units along the desired fold lines. These can be applied by a web manufacturer and exist in the web of the original source roll, or can be added by a particular utilization device in the system. A prior art folder is shown and described in U.S. Pat. No. 5,558,318, entitled SEPARATOR FOR FORMING DISCRETE STACKS OF FOLDED WEB, by H. W. Crowley, et al., the teachings of which are expressly incorporated herein by reference. This folder is designed to create short discrete stacks that are drawn away by a conveyor belt, or a continuous flow (“waterfall”) of folded web that must be collected into a larger-height stack at a location remote from the conveyor.
When a folder completes a stack of web, based either on completing a particular job, or reaching a maximum stack height, the upstream end of the folded web stack is typically separated from the downstream folded stack by a cutter unit and the stack is driven away from the folder before a new stack can be formed. Often, the process of vacating the existing stack is cumbersome, as a large completed stack may weigh several hundred pounds and extend over four feet high. Various devices and conveyances for handling such large stacks are taught in U.S. Pat. No. 6,120,043, entitled METHOD AND APPARATUS FOR BUSINESS FORMS PROCESSING, by H. W. Crowley, et al., the teachings of which are expressly incorporated herein by references. This reference relates to the receipt of a waterfall of folded continuous web onto a tilting table from a folder (such as the folder referenced above) and forming a stack on the table, which is subsequently transferred to various carts and dollies for later processing and/or use. As is clear by the description of the reference, the formation and handling of large stacks of folded web typically entails many stack formation and handling components and fairly involved handling processes that (while being simple and reliable) may entail interruptions in the process streams while downstream stack handling is accomplished.